1. Field of the Invention
The present invention relates to a laminated coil component such as a chip inductor and a method for manufacturing the same.
2. Description of the Related Art
In general, laminated coil components, such as chip inductors, include ceramic films and coil conductors having half-turn shapes which are laminated on one another as shown in Japanese Unexamined Patent Application Publication No. 2003-209016. In such a laminated coil component, both ends of the respective coil conductors are connected to one another through via-hole conductors, whereby a spiral coil is obtained.
With respect to such laminated coil components, in recent years, there have been demands for a reduction in the size and the height of the coil components and for improvements in the characteristics thereof. In order to meet these demands, the coil conductors have reduced line widths and increased thicknesses, the ceramic films have reduced thicknesses. However, as the thickness of the ceramic films is reduced, stress is concentrated on portions in which via-hole conductors overlap one another in a laminated body, which results in a deterioration in an inductance characteristic and an impedance characteristic, and furthermore, short-circuits among the via-hole conductors are more likely to occur.
FIG. 7 shows a sectional view of such a laminated coil component. Pad portions 56 having relatively large widths are arranged on end portions of coil conductors 55 each of which is interposed between ceramic films 51 so that a connection characteristic is improved. Interlayer connections among the coil conductors 55 are provided through the pad portions 56 and via-hole conductors 57. Furthermore, external electrodes 60 are disposed on both ends of a laminated body. FIG. 8 is an enlarged view illustrating the interlayer connection.
The pad portions 56 have relatively large areas, and the pad portions 56 and the via-hole conductors are produced concurrently by the application of conductive paste. Therefore, the conductive paste is likely to be applied thicker in the portions at which the pad portions 56 and the via-hole conductors 57 overlap one another than in the coil conductors 55, and stress is concentrated on these overlapping portions. Accordingly, an inductance is deteriorated, and defects due to short-circuiting frequently occur. Furthermore, projection portions 59 are generated on the laminated body as shown in FIG. 7, which causes problems when mounting the laminated coil component.